Intrinsic difference in Schottky barrier effect for device configuration of organic thin-film transistors

Schottky barrier effect for n-channel organic thin-film transistors (OTFTs) with bottom-gate, top-contact (TC) and bottom-gate, bottom-contact (BC) configuration was examined by using device simulation with a thin-film organic transistor advanced simulator (TOTAS). A thermionic field emission (TFE) model which addresses tunneling of thermally excited electrons was applied as a carrier injection model of OTFTs. Simulation results reveal that the BC configuration is affected by Schottky barrier more severely than the TC configuration under the same condition for device parameters, and that this discrepancy in device characteristics can be completely alleviated by contact-area-limited doping, where highly-doped semiconducting layers are prepared in the neighborhood of contact electrodes. Moreover, the existence of an intrinsic Schottky barrier is indicated even though an ohmic-contact condition is assumed, which becomes more prominent for lower bulk carrier concentration in organic semiconductor. This work suggests the availability of the TFE model for simulating realistic OTFT devices with Schottky contacts. From the simulation results, intrinsic differences in device performance for the TC and BC configurations are discussed.